Photoelectric converter with light shielding sections

ABSTRACT

A photoelectric converter comprised of a semiconductor transistor comprises two semiconductor regions of same electroconductive type and a semiconductor region of opposite electroconductive type to that of the two semiconductor regions. The semiconductor region of opposite electroconductive type is irradiated with a light. An amplified power is output from at least one of the two semiconductor regions of same electroconductive type. The semiconductor region of the opposite electroconductive type comprises a semiconductor region that accumulates a charge generated by light input and a semiconductor region acting as a control electrode region for the semiconductor transistor.

This application is a division of application Ser. No. 07/860,121 filedMar. 31, 1992 which is a continuation of application Ser. No. 07/711,389filed Jun. 6, 1991, abandoned, which is a continuation of applicationSer. No. 07/600,242 filed Oct. 22, 1990, abandoned, which is acontinuation of application Ser. No. 07/363,058 filed Jun. 6, 1989abandoned; application Ser. No. 07/860,121 now being U.S. Pat. No.5,245,203.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a photoelectric converter and moreparticularly to a photoelectric converter capable of amplifyingphotoelectrically converted power, which comprises a light-receivingsection and a light-shielding section, or a photoelectric converter of asemiconductor transistor, which comprises two semiconductor regions ofsame electroconductive type and a semiconductor region of oppositeelectroconductive type to that of the two semiconductor regions, wherethe semiconductor region of opposite electroconductive type isirradiated with light and an amplified power is output from at least oneof the two semiconductor regions of same electroconductive type.

2. Related Background Art

A photoelectric converter which accumulates, a charge generated by lightirradiation and outputs an amplified power corresponding to theaccumulated charge is one type of photoelectric converters for use in apicture reading device in a facsimile machine, a copying machine, etc.One particular of such photoelectric converters is a photoelectricconverter which accumulates carriers (holes) in a base region of aphototransistor by light irradiation of the base region and outputs anamplified electric current from an emitter region, where the base regionof the phototransistor is formed as a light-receiving section and theemitter region as a light-shielding section. A photoelectric converterusing a phototransistor can amplify carriers in the light-receivingregion, increase sensitivity, reduce random noise and increase S/Nratio, as compared with a photoelectric converter using a photodiode andhaving no function to amplify a photoelectric current.

FIG. 1 is a schematic cross-sectional view of a conventionalphotoelectric converter, where numeral 1013 is an n-type layerfunctioning as a collector of phototransistor, 1003 is an n-epitaxiallayer functioning, 1005 is a p layer as a base region of thephototransistor, 1006 is an n layer functioning as an emitter region ofthe phototransistor, 1007-2 is an emitter electrode made of A1, etc.,1008 is a LOCOS oxide film, L is a light-receiving section and D is alight-shielding section.

When such photoelectric converters are used in a color line sensor 1101,as shown in FIG. 2, three line sensors are provided for red (R), green(G) and blue (B), where each line sensor comprises a light-shieldingsection 1011 and a light-receiving section 1012. The length of thelight-shielding section 1011 and that of the light-receiving section1012 in the line sensor arrangement direction, i.e., direction A in FIG.2, are n bits and one bit, respectively. One bit corresponds to thelight-receiving section of one sensor cell and is in a rectangularshape, whose one side is, for example, 10 μm long.

The respective line sensors corresponding to R, G and B are positionallydifferent from one another, and thus when a signal R is obtained at agiven line of the a manuscript, a signal G is a signal at a position of(n+2)th line from the given line and a signal B is a signal at aposition of the (2n+3)th line from the given line. In order to obtainsignals R, G and R at the same position of the manuscript, at least thepreviously output signals G and B must be stored in an external memory102 through the respective sample hold circuits (S/H) 1014 and A/Dconversion circuits 1015 among the signals R, G and B.

Such photoelectric converters are disclosed, for example, in Laid-OpenEuropean Patent Application No. 0132076.

FIG. 3A is a schematic plan view showing the structure of aphotoelectric converter in detail and FIG. 3B is a schematiccross-sectional view showing the line A--A' of FIG. 3A, wherephotoelectric converter cells are arranged on an n silicon substrate3201, and each cell is electrically insulated from the adjacent cellsthrough device-separating regions 3202 comprising SiO₂, Si₃ N₄,polysilicon or the like. Each cell has the following structure. A p baseregion 3204 and a p region 3205 are formed on an n⁻ region 3203 with alow impurity concentration, formed by an epitaxial technique, etc.,through doping with p-type impurity such as boron, etc., and an n⁺emitter region 3206 is formed on the p base region 3204. The p baseregion 3204 and the p region 3205 also act as a source and a drain of ap channel MOS transistor as will be described later.

An oxide film 3207 is formed on the n⁻ region 3203 having the thusformed subregions, and a gate electrode 3208 and a capacitor electrode3209 of the MOS transistor are formed on the oxide film 3207. Thecapacitor electrode 3209 is counterposed to the p base region 3204through the oxide film 3207 to form a capacitor for controlling the basepotential.

In addition, an emitter electrode 3210 connected to the n⁺ emitterregion 3206 and an electrode 3211 connected to the p region 3205 arefurther formed, and a collector electrode 3212 is formed on the backside of the substrate 3201 through an ohmic contact layer.

The operations of the photoelectric converter cell will be describedbelow. Light is input into the photoelectric converter cell from theside of the p base region 3204 and carriers (in this case holes) areaccumulated in the p base region 3204 in an amount corresponding to thelight quantity (accumulation operation).

The base potential changes with the accumulated carriers and anelectrical signal corresponding to the input light quantity is read outby reading the potential change through the emitter electrode 3210(reading operation).

A refresh operation to remove the holes accumulated in the p base region3204 will be described below.

FIGS. 4A and 4B show potential wave forms for explaining the respectiverefresh operation. As shown in FIG. 4A, an MOS transistor is broughtinto an ON state only when a negative potential higher than thethreshold value is applied to the gate electrode 3208. As shown in FIG.4B, the emitter electrode 3210 is earthed and the electrode 3211 isbrought to an earth potential to carry out refresh operation. Then, anegative potential is applied to the gate electrode 3208 at first to putthe p channel MOS transistor in an ON state, whereby the potential of pbase region 3204 can be kept at a constant value, irrespective of theaccumulated potential level. Then, a positive potential pulse forrefresh operation is applied to the capacitor electrode 3209, wherebythe p base region 3204 is biased in the forward direction to the n⁺emitter region 3206 and the accumulated holes are removed through theearthed emitter electrode 3210. At the time of rising of the refreshpulse, the p base region 3204 is returned to the initial state ofnegative potential (refresh operation). After the potential of the pbase region 3204 is made constant by the MOS transistor, the residualcharge is erased by the application of the refresh pulse in this manner,and thus a fresh accumulation operation can be carried out again,independently of the previously accumulated potential. Furthermore, theresidual charge can be rapidly erased and thus a high speed operationcan be carried out. Thereafter, the accumulation operation, readingoperation and refresh operation are likewise repeated.

The potential Vp generated in the base by the holes accumulated in thebase by photoexcitation can be given by the following formula:

    Vp=Q/C

where Q is a charge amount of holes accumulated in the base and C is acapacitance connected to the base. As is obvious from the formula, ahigh level of integration can reduce the cell size and also reduce bothQ and C, and thus the potential Vp generated by photoexcitation can bekept substantially constant. Thus, the system proposed above is alsoadvantageous for higher resolution. However, a higher blue sensitivityand a higher response speed of the semiconductor transistor have beensometimes required for the foregoing photoelectric converter and thus afurther improvement of the characteristics has been desired.

When a picture treatment is carried out with the color line sensor 1101as explained, referring to FIGS. 1 and 2, a higher capacity of theexternal memory than a given one is required for storing the previouslyoutput signals G and B in the external memory so as to obtain signals R,G and B at the same position of a draft, and a reduction of thenecessary memory capacity has been desired on account of cost reduction,etc. Furthermore, there has been a problem of difficult optimization inthe base region of a phototransistor because the optimum conditions ofthe size, impurity concentrations, etc. in the photoelectric conversionregion are different from those for a bipolar transistor, and a furtherimprovement thereof has been also desired.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a photoelectricconverter of higher sensitivity, particularly higher blue sensitivity,capable of high speed response to an input signal.

Another object of the present invention is to provide a photoelectricconverter capable of optimizing a sensor section and a switching sectionand more particularly optimizing the optimum conditions in the baseregion of a phototransistor and those for a bipolar transistor.

Another object of the present invention is to provide a photoelectricconverter with an enhanced degree of freedom in system design andoptical design and with design simplification.

Still another object of the present invention is to provide aphotoelectric converter of a semiconductor transistor, which comprisestwo semiconductor regions of same electroconductive type and asemiconductor region of opposite electroconductive type to that of thetwo semiconductor regions, where the semiconductor region of oppositeelectroconductive type is irradiated with light and an amplified poweris output from at least one of the two semiconductor regions of sameelectroconductive type, and the semiconductor region of the oppositeelectroconductive type comprises a semiconductor region that accumulatesa charge generated by light input and a semiconductor region acting as acontrol electrode region for the semiconductor transistor.

A further object of the present invention is to provide a photoelectricconverter capable of amplifying a photoelectrically converted power,which comprises a light-receiving section and a light-shielding section,a photoelectric conversion part being formed in the light-receivingsection, an amplifying part being formed in the light-shielding section,the photoelectric conversion part being connected to an input region ofthe amplifying part through a wiring, and the light-receiving sectionbeing formed separate from the light-shielding section at apredetermined distance.

A still further object of the present invention is to provide aphotoelectric converter which comprises a first semiconductor region offirst electroconductive type, a second semiconductor region of firstelectroconductive type provided on the first semiconductor region, athird semiconductor region of second electroconductive type provided incontact with the second semiconductor region, a fourth semiconductorregion of second electroconductive type provided in contact with thethird semiconductor region and the second semiconductor region, a fifthsemiconductor region of first electroconductive type provided in contactwith the fourth semiconductor region, and a sixth semiconductor regionof second electroconductive type provided in contact with the secondsemiconductor region, the third semiconductor region being destined to alight input region and the first, second, fourth and fifth semiconductorregions and the second, fourth and sixth semiconductor regions beingdestined to elements constituting transistors, respectively.

A still further object of the present invention is to provide aphotoelectric converter which comprises a first semiconductor region offirst electroconductive type, a second semiconductor region of the firstelectroconductive type provided in contact with the first semiconductorregion, a third semiconductor region of a second electroconductive typeprovided in contact with the second semiconductor region, a fourthsemiconductor region of the second electroconductive type electricallyconnected to the third semiconductor region through an electroconductivematerial and provided in contact with the second semiconductor regionand a fifth semiconductor region of the first electroconductive typeprovided in contact with the fourth semiconductor region, the thirdsemiconductor region being destined to be a light input region and thefirst, second, fourth and fifth semiconductor regions are destined to bean element constituting a transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view explaining the structure of aconventional photoelectric converter.

FIG. 2 is a schematic structural view explaining an image reading systemusing a conventional photoelectric converter.

FIG. 3A is a schematic plan view of the structure of a conventionalphotoelectric converter and FIG. 3B is a schematic cross-sectional viewalong the line A--A' of FIG. 3A.

FIGS. 4A and 4B show potential wave forms for explaining a conventionalrefresh operation, respectively.

FIGS. 5A and 5B are schematic structural views explaining aphotoelectric converter according to a first embodiment of the presentinvention, where FIG. 5A is a schematic plan view and FIG. 5B is aschematic cross-sectional view along the line A--A' of FIG. 5A.

FIG. 6A is a schematic, enlarged view when cut away along the line B--B'of FIG. 5B, and FIG. 6B is a potential profile in the depth direction ofFIG. 6A.

FIG. 7 is a characteristic diagram explaining the absorption ratio of Siand Ge to the light wavelength.

FIG. 8 is a characteristic diagram explaining a relationship betweenp-region concentration NA and whole depletion layer thickness Xp at areverse bias potential VR=5V.

FIG. 9 is a characteristic diagram explaining a relationship betweenp-region concentration NA and p-layer depletion layer thickness Xp.

FIG. 10 is a schematic circuit diagram explaining one embodiment of thedriving circuit of a photoelectric converter according to the presentinvention.

FIG. 11 is a schematic cross-sectional view explaining a photoelectricconverter according to a second embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view explaining a photoelectricconverter according to a third embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view explaining a photoelectricconverter according to a fourth embodiment of the present invention.

FIG. 14 is a schematic cross-sectional view explaining a photoelectricconverter according to a fifth embodiment of the present invention.

FIG. 15 is a schematic cross-sectional view explaining a photoelectricconverter according to a sixth embodiment of the present invention.

FIG. 16 is a schematic cross-sectional view explaining a photoelectricconverter according to a seventh embodiment of the present invention.

FIG. 17 is a schematic structural view explaining a picture readingsystem used in the present phoeoelectric converter.

FIG. 18 is a schematic structural view explaining one example of apicture reading apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present photoelectric converter capable of attaining theforegoing objects, a semiconductor region of opposite electroconductivetype is divided into a semiconductor region that accumulates a chargegenerated by light input and a semiconductor region that serves as acontrol electrode region of a semiconductor transistor, whereby thepreparation conditions such as impurity concentration, thickness, etc.of the semiconductor region that accumulates a charge generated by lightinput and the preparation conditions such as impurity concentration,impurity concentration distribution, thickness, etc. in thesemiconductor region acting as a semiconductor transistor controlelectrode region can be optimized in the respective semiconductorregions, as desired.

Furthermore, in the present photoelectric converter capable of attainingthe foregoing objects, a photoelectric conversion part is formed in thelight-receiving section, an amplifying part is formed in thelight-shielding section, the photoelectric conversion part is connectedto an input region of the amplifying part by a wiring, and thelight-receiving section is provided separate from the light-shieldingsection at a predetermined distance, whereby the present photoelectricconverter can be provided with an amplifying function and thelight-receiving sections can be formed adjacent to each other, whileproviding the light-receiving sections separate from the light-shieldingsections.

The present invention will be described in detail below, referring tothe embodiments and drawings.

FIGS. 5A and 5B are schematic structural views explaining aphotoelectric converter according to the first embodiment of the presentinvention, where FIG. 5A is a schematic plan view of a photoelectricconverter cell and FIG. 5B is a schematic vertical cross-sectional viewalong the line A--A' of FIG. 5A.

As shown in FIGS. 5A and 5B, the photoelectric converter cell comprisesa silicon substrate 4001, doped with atoms of Periodic Table Group V,such as phosphorous (P), antimony (Sb), arsenic (As), etc. as animpurity to make the substrate d-type, or a silicon substrate 4001,doped with an atom of Periodic Table, Group III, such as boron (B),aluminum (Al), etc. as an impurity to make the substrate p-type, anembedded region (n⁺) 4002 formed on the substrate 4001, an n⁻ region4003 with a low impurity concentration formed on the embedded region4002 by epitaxial technique, etc., a p⁻ region 4004 of a light-receivingsection, doped with an impurity such as boron (B), etc. formed on the n⁻region 4003 by impurity diffusion, ion diffusion, epitaxial technique,etc., a p⁺ region 4005 as a base for a bipolar transistor and as asource for an MOS transistor, formed by the same technique as used forforming the p⁻ region 4004, an n⁺ region 4006 as an emitter for thebipolar transistor, formed in the p⁺ region 4005, a p⁺ region 4007 as adrain for the MOS transistor, an n⁺ region 4008 as a channel stop, an n⁺region 4009 for lowering the collector resistance of the bipolartransistor, an electrode 4101 of polysilicon, a metal, etc. as a gatefor the MOS transistor, an electrode wiring 4108 connected to theelectrode 4101, electrode wiring 4102, 4103, and 4104 of polysilicon, ametal, etc. connected to the emitter for the bipolar transistor, anelectrode wiring 4109 connected to the drain for the MOS transistor, anelectrode wiring 4110 connected to the n⁺ region 4009, and insulatingfilms 4105, 4106, and 4107 for separating the electrodes, wiring anddevices from one another.

For simplification, the insulating films 4105, 4106 and 4107 and theelectrode wiring are omitted in FIG. 5A.

Working of the present photoelectric converter will be described below.

FIG. 6A is a schematic enlarged cross-sectional view along the lineB--B' of FIG. 5B and FIG. 6B is a potential diagram in the depthdirection of FIG. 6A, i.e. the lateral direction of FIG. 6A.

In FIG. 6A, W is a depletion layer thickness, Xp and Xn are depletionlayer thickness in the p⁻ region 4 and the n⁻ region 3, respectively,and Xj is a depth of p⁻ region 4.

In FIG. 6B, W is a depletion layer thickness and Xd is a neutral regionthickness in the p⁻ region 4.

When light absorption takes place in the depletion layer (wherein thedepletion layer thickness W), electrons and holes thus formed morerapidly migrate by drift without any recombination thereof, and thus ahigher photosensitivity can be maintained. When light absorption takesplace in the neutral region (within the neutral region thickness Xd) onthe other hand, the thus formed electrons migrate by diffusion andrecombine with holes, and thus the photosensitivity is lowered. Thus, itis preferable that in the light-receiving section the neutral region issmaller on the surface. However, when the surface is depleted, carriersare formed on the boundary between the semiconductor and the insulatinglayer, irrespective of light input, producing a noise. Thus, it ispreferable that the surface is in a neutral region.

FIG. 7 is a characteristic diagram explaining an absorption ratio of Sior Ge to the light wavelength. As shown in FIG. 7, an absorption ratioof Si or Ge in larger with a shorter wavelength. In case of Si, theabsorption ratio is up to 2×10⁴ cm⁻¹ for the blue color (λ=0.45 μm), upto 7.5×10³ cm⁻¹ for the green color (λ=0.53 μm), and up to 3×10³ cm⁻¹for the red color (λ=0.65 μm). When the colors allow for a half-width ofabout 0.05 μm, the light absorption in Si can be thoroughly carried outin depth of up to 1 μm for the blue color, up to 2 μm for the greencolor and up be 5 μm for the red color. Thus, the blue color is mostinfluenced with the neutral region thickness Xd on the semiconductorsurface, and the sensitivity is lowered, depending upon the thickness.

The depletion layer width can be given by the following equation.##EQU1## where W: depletion layer thickness

Xp: p⁻ region depletion layer thickness

NA: p⁻ region impurity concentration

ND: n⁻ region impurity concentration

εS: dielectric constant

ni: true carrier concentration

VR: reverse bias potential

FIG. 8 is a characteristic diagram showing a relationship between the p⁻impurity concentration NA and the whole depletion layer thickness W at areverse bias potential of VR=SV. In FIG. 8, the axis of abscissa shows ap⁻ impurity concentration NA, the axis of ordinate shows a wholedepletion layer thickness W and parameters show n⁻ region impurityconcentrations ND. For example, in order to efficiently detect all ofblue, green and red colors, a whole depletion layer thickness of about 5μm is required. In that case, it is obvious from FIG. 8 that ND must beless than 2×10¹⁴ cm⁻³.

Spectrosensitivity of the photoelectric converter can be approximatelyshown by the following equation. ##EQU2## where λ: light wavelength

α: light absorption ratio (cm⁻¹)

Xd: non-sensitive region (neutral region)

W: high sensitivity region (depletion layer thickness)

T: ratio of light quantity input inks the transistor (transmissivity)

As is obvious from the foregoing equation (4), the sensitivity issharply influenced with the thickness of Xd, and thus a smallerthickness is preferable for Xd. Furthermore, the sensitivity isdependent upon the wavelength, and the blue color is lower in thesensitivity than the red color. In order to correct the relativespectrosensitivity, W is decreased. In this way, the sensitivity can beoptimized.

As is readable from FIG. 8, the sensitivity can be optimized bycontrolling the n⁻ region concentration. In order to increase thesensitivity for blue color, it is preferable to decrease the neutralregion Xd.

FIG. 9 is a characteristic diagram explaining a relationship between thep⁻ impurity concentration NA and the p-layer depletion layer thicknessXp, where the axis of abscissa shows a p⁻ impurity concentration NA, theaxis of ordinate shows a p-layer depletion layer thickness Xp andparameters shows n-region impurity concentrations ND. In FIG. 9, whenp-region NA is 10¹⁵ cm⁻³ at ND=10¹⁴ cm⁻³, Xp is 0.6 μm.

When Xj of p⁻ region 4 is 0.7 μm, the non-sensitive region can have athickness of 0.1 μm, and an optimization to increase the sensitivity forblue color can be made. By making an impurity concentration higher onlyin a region to a thickness of 0.1 μm from the surface and lower in aregion over the thickness of 0.1 μm from the surface, the region overthe thickness of 0.1 μm from the surface can be depleted.

In the present invention, the p⁻ region of the light-receiving sectionthat accumulates the charge generated by light input is providedseparate from the p⁺ region that acts as a base region for a bipolartransistor, whereby the light-receiving surface can be made to maintaina neutral region and the deeper region than the surface neighborhood canbe depleted. The whole depletion layer thickness can be selected toconform to the spectrosensitivity requirements, and the n⁻ regionconcentration can be selected thereby.

FIG. 10 is a schematic circuit diagram explaining one example of adriving circuit for the present photoelectric converter. In thisexample, a line sensor, where sensors S (S1, S2 . . . ) are arranged ina linear state, is illustrated. Each of the sensors S (S1, S2 . . . )comprises a bipolar transistor and a reset transistor Q_(res) connectedto the base of the bipolar transistor. Carriers excited by light inputare accumulated in the base of bipolar transistor, and read out at theemitter. By turning Q_(res) on, the sensor is reset to a constantpotential.

A pulse φ_(res) is input to the gate electrode at Q_(res) of each ofsensors S1, S2, . . . for ON/OFF control, whereas a constant potentialVbg is applied to other main electrode of Q_(res).

A constant positive potential is applied to the collector electrode ofeach of sensors S (S1, S2, . . . ), and the emitter electrodes are eachconnected to vertical lines L (L1, L2 . . . ).

A constant potential Veg is applied to each of vertical lines L (L1, L2. . . ) through transistors Q_(vrs) and a pulse φ_(res) is input to thegate electrode of Q_(vrs) for ON/OFF control.

Furthermore, the respective vertical lines L (L1, L2, . . . ) are eachconnected to capacitors for accumulation, and signals are output frombipolar transistors BPT2 through transistors Qt.

The present photoelectric converter will be further described below,referring to further embodiments, where the same constituent members asshown in FIGS. 5A and 5B are identified with the same reference numeralsand symbols as used in FIGS. 5A and 5B and their explanation is omitted.

FIG. 11 is a schematic cross-sectional view showing a photoelectricconverter according to a second embodiment of the present invention,where a p⁺ region 4010 is provided only on the surface of the p⁻ region4004 as a light-receiving region and an n region 4011 of high impuritydensity is provided below the base of the bipolar transistor to lowerthe collector resistance.

FIG. 12 is a schematic cross-sectional view explaining a photoelectricconverter according to a third embodiment of the present invention,where the p⁻ region 4004 as a light-receiving region is extended underthe emitter of the bipolar transistor and the bipolar transistor is madein a drift base form to attain a high speed response. Needless to say,the bipolar transistor BPT2 at the output side, as shown in FIG. 10 canalso take the same structure as mentioned above.

FIG. 13 is a schematic cross-sectional view explaining a photoelectricconverter according to a fourth embodiment of the present invention,where the n region 4011 is made thicker to reach the embedded region,thereby lowering the collector resistance.

FIG. 14 is a schematic cross-sectional view explaining a photoelectricconverter according to a fifth embodiment of the present invention,where the embedded region is restricted only to the site for a bipolartransistor, etc. As shown in FIG. 14, no neutral region can be made toexist between the n⁻ region of a light-receiving section and the psubstrate by design, thereby eliminating a cause for carrier diffusionin the lateral direction between the sensor cells and also improving thesmear and NTF.

In the foregoing embodiments, not only Si but also other semiconductormaterials can be used and also an interchanged structure of all of n andp can be also used.

As shown in the foregoing embodiments, the transistor characteristics,more particularly amplifying characteristics, switching characteristics,etc. of transistors, can be improved by lowering the collectorresistance.

In the foregoing embodiments, the abovementioned objects of the presentinvention can be more effectively attained.

FIG. 15 is a schematic cross-sectional view explaining a photoelectricconverter according is a sixth embodiment of the present invention. Thisembodiment relates to a photoelectric converter with a photodiode anodeand a bipolar transistor base region prepared by separate steps.

In FIG. 15, numeral 1001 is a p-type substrate; 1002 is a n-typeembedded layer as a bipolar transistor collector; 1003 is an n⁻epitaxial layer; 1004 is a p layer of a bipolar transistor base regionas an amplifying part; 1005 is a p layer of a photodiode anode as aphotoelectric conversion part; 1006 is an n layer as a bipolartransistor emitter region; 1007-1 is a wiring made of anelectroconductive material such as A1, etc. to connect the p layer 1005of photodiode anode to the p layer 1004 of bipolar transistor baseregion; 1007-2 is an emitter electrode made of an electroconductivematerial such as Al, polysilicon, etc.; 1008 is a LOCOS oxide film; Lshows a light-receiving section; and D shows a light-shielding section.

As shown in FIG. 15, the photodiode provided in the light-receivingsection and the bipolar transistor provided in the light-shieldingsection are connected to each other through the wiring 1007-1 and thelight-receiving section and the light-shielding section can be providedseparate from each other at a predetermined distance.

When the present photoelectric converter is used as a color line sensor,the light-shielding section of a green line sensor can be providedoutside a blue (or red) line sensor among line sensors for red (R),green (G) and blue (B), as shown in FIG. 17, and the light-receivingsection for red and the light-receiving section for green can beprovided adjacent to each other. Thus, at the time of obtaining an Rsignal in a given line of a draft, a G signal is a signal at a positionof the draft in the 2nd line from the given line and a B signal is asignal at a position of the draft in the (n+3)th line from the givenline, and thus the quantity of previously output G and B signals to bememorized is smaller than that by the color line sensor as shown in FIG.2, and the capacity of the external memory can be made much smaller.

In this embodiment, the p layer 1004 of a bipolar transistor base regionand the p layer 1005 of a photodiode anode are independently controlledwith respect to the impurity diffusion, and the size of diffused region,impurity concentration, etc. can be independently controlled. Thus, thespectrosensitivity characteristics of photodiode can be adjusted to adesired wavelength sensitivity and also characteristics of bipolartransistor such as a amplification ratio, response speed, etc. can beset to desired optimum values.

FIG. 16 is a schematic cross-sectional view explaining a photoelectricconverter according to a seventh embodiment of the present invention,where a p⁺ region is formed in the bipolar transistor and a collectorregion of bipolar transistor is provided separately, and the sameconstituent members as in the sixth embodiment are identified with thesame reference numerals and symbols and their explanation is omitted.

In FIG. 16, numeral 1004₋₁ is a p layer of a photodiode anode and 1004₋₂is a p layer of a bipolar transistor base region, and they are preparedat the same time. Numeral 1006₋₋₂ is an n layer of bipolar transistoremitter region and 1009 is a p⁺ layer, provided with a high impurityconcentration region to improve the frequency characteristics. Numeral1010 is an n layer of bipolar transistor collector region, 1006₋₃ is ann⁺ layer and 1007₋₃ is a collector electrode made of anelectroconductive material such as A1, polysilicon, etc.

As shown in FIG. 16, the photodiode provided in the separately formedlight-receiving section and the bipolar transistor provided in thelight-shielding section are connected to each other through a wiring1007₋₁ to attain the same effect as in the sixth embodiment and also tomake a color line sensor as shown in FIG. 17.

An example of a picture reading apparatus using the presentphotoelectric converter will be given below.

FIG. 18 is a schematic structural view explaining one example of apicture reading apparatus, where a draft 5201 is mechanically moved inthe arrow-marked Y direction relative to a reading member 5205 andreading of a picture is carried out by an image sensor 5204 throughscanning in the arrow-marked X direction.

At first, a light from a light source 5202 is reflected on the draft5201 and the reflected light passes through an image-forming opticalsystem 5203 to form an image on an image sensor 5204 as the presentphotoelectric converter. Then, carriers corresponding to the intensityof input light are accumulated in the image sensor 5204 andphotoelectrically converted and output as an image signal. The imagesignal is subjected to a digital conversion in an AD converter 5206 andinput into the memory in a picture processing unit 5207 as image data.After treatments such as shading correction, color correction, etc., theimage data are transmitted to a personal computer 5208, a printer, etc.

After the completion of image signal transmission based on the scanningin the X direction, the draft 5201 is moved relative to the Y direction,and the same operations as in the foregoing operations are repeated,whereby the entire picture on the draft 5201 can be converted toelectrical signals to output picture information.

As explained in detail above, the present photoelectric converter canhave an amplifying function and the light-receiving section and thelight-shielding section can be provided separate from each other and thelight-receiving sections can be provided adjacent to each other. Thus,in the present invention, system design and optical design can besimplified.

Furthermore, in the present photoelectric converter, the input region ofthe amplifying part can be provided independent from the photoelectricconversion part, and the size, impurity concentration, structure, etc.of diffusion region can be independently controlled to adapt thespectrosensitivity characteristics of the photoelectric conversion partto a desired wavelength sensitivity and also to set characteristics ofthe amplifying part such as amplification ratio, response speed, etc. todesired optimum values. Thus, a device with desired properties can bedesigned.

Furthermore, in the present photoelectric converter, the optimumpreparation conditions such as an impurity concentration, thickness,etc. of a semiconductor region for accumulating the charge generated bylight input and the optimum conditions such as an impurityconcentration, impurity concentration distribution, thickness, etc. of asemiconductor region that acts as a semiconductor transistor controlelectrode region can be selected as desired in the respectivesemiconductor regions. Thus, the light-receiving section and thesemiconductor transistor section can be separately designed to enhanceblue color sensitivity and attain a higher speed semiconductortransistor response.

We claim:
 1. An image processing apparatus comprising:a plurality ofphotoreceiving sections, each of which includes a plurality ofphotoreceiving elements arranged in a line; light shielding sectionsprovided along said photoreceiving sections for deriving signals fromthe photoreceiving sections; a signal processing section for processingthe signal derived from each said photoreceiving section; and a memorysection for storing the signal processed by each said signal processingsection; wherein at least two of said photoreceiving sections arrangedin the line are adjacent to each other, and said light shieldingsections relating to said photoreceiving sections are arranged on sidesopposite to a side at which said photoreceiving sections are adjacenteach other.
 2. An apparatus according to claim 1, whereinsaidphotoreceiving sections are line sensors which correspond, at least, tored, green and blue (RGB).
 3. An apparatus according to claim 1,whereinsaid signal processing section is one of a sample and holdcircuit and an A/D conversion circuit.
 4. An apparatus according toclaim 1, whereinsaid memory is an external memory.
 5. An apparatusaccording to claim 1, further comprising a light source for illuminatingan original including information to be read.
 6. An apparatus accordingto claim 1, further comprising optical means for imaging informationinputted into said photoreceiving section.
 7. An apparatus according toclaim 1 whereinsaid memory section is provided in an image processingsection.
 8. An apparatus according to claim 7, whereinsaid imageprocessing section has one of a shading and a color correction function.9. An apparatus according to claim 1, further comprising moving meansfor relatively moving said photoreceiving section and an originalincluding information to be read.
 10. An apparatus according to claim 1,whereinsaid light shielding section has a width twice as large as awidth of said photoreceiving section.
 11. An apparatus according toclaim 1, whereinsaid photoreceiving sections and said light shieldingsections are arranged at least alternatively, in an order of said lightshielding section, said photoreceiving section, said photoreceivingsection, and said light shielding section.
 12. An apparatus according toclaim 11, whereinsaid photoreceiving sections and said light shieldingsections are arranged in an order of reading information.
 13. Aphotoelectric conversion apparatus comprising:plural line sensors eachhaving a photoreceiving section, in which plural photoreceiving elementsare arranged in a line, and a light shielding section, provided alongsaid photoreceiving section of each said line sensors for derivingsignals from the photoreceiving elements of the photoreceiving sections;wherein said line sensors are arranged so that the photoreceivingsection of one line sensor is at least one of (a) adjacent to thephotoreceiving section of another line sensor adjacent to the one linesensor, and (b) adjacent to the light shielding section of another linesensor adjacent to the light shielding section of the one line sensor.14. An apparatus according to claim 13, whereinsaid line sensors havethe photoreceiving sections for reading information corresponding, atleast, to red, green and blue.
 15. An apparatus according to claim 13,whereinthe photoreceiving sections and the light shielding sections arearranged alternatively in an order of the light shielding section, thephotoreceiving section, the photoreceiving section, and the lightshielding section.